1. Field of the Invention
The present invention relates to an LCD monitor with a dual interface and a control method thereof, and more particularly, to an LCD monitor which can display a system booting screen, even if a video signal input when a computer system is in system booting mode is unfit for a preset display mode.
2. Description of the Related Art
An LCD (liquid crystal display) monitor occupies a relatively small space in comparison with a CRT (cathode ray tube) monitor, and has a digital interface which can directly process digital data output from a computer main body without signal loss, thereby realizing a high definition picture. However, the CRT monitor processes only analog data, and therefore a graphic card applied to the CRT monitor must convert the digital data into the analog data before transmitting data to the CRT monitor.
To make the graphic card for the CRT monitor compatible with the LCD monitor, there has been proposed an LCD monitor having a dual interface for digital and analog data. A DVI-I (digital video interface-I) interface is an example of the dual interface, and the LCD monitor can process both digital and analog data through the DVI-I interface. Thus, the LCD monitor having the dual interface is operated in an analog display mode or a digital display mode which is previously set by a user according to the graphic card, or is operated in a default mode in the absence of a preset display mode.
As a digital graphic card to output a digital video signal, there is proposed a graphic card which outputs an analog video signal when a computer system is in BIOS (basic input/output system) booting, and outputs a digital video signal after WINDOWS® booting. In the case of the graphic card, a user sets the LCD monitor to be operated in the digital display mode, so that the LCD monitor cannot display a BIOS-booting screen because the analog signal is output when the computer system is in BIOS-booting. Herein, BIOS-booting and WINDOWS® booting are collectively called system booting.
FIG. 4 is a flow diagram of the LCD monitor having the conventional dual interface. In the LCD monitor wherein the display mode is the digital display mode, set by the user or as a default mode, when the computer main body and the LCD monitor are turned on (P10), the computer main body starts the system booting (P12). During the system booting, the computer main body transmits a system booting video signal to the LCD monitor so as to display the system booting screen. Herein, the system booting video signal is output as an analog signal or a digital signal according to the graphic card.
Then, because the LCD monitor is turned on under the digital display mode, the LCD monitor determines whether a system booting video signal is input through a digital video signal port or not (P14).
When the system booting video signal is output from the computer main body as the digital signal, the LCD monitor processes the system booting video signal under the digital display mode (P16), and displays the system booting screen (P18).
However, when the system booting video signal is output from the computer main body as an analog signal, the LCD monitor enters a DPMS (display power management signaling) mode because the LCD monitor cannot receive the digital signal (P20). In this case, the user cannot see the system booting screen, and therefore cannot check the state of the computer system.
Particularly, in the case in which the user uses a computer system which is set to require a password for security while the system is booting, a user must input the password through a monitor operating under the analog display mode, and use another monitor operating under the digital display mode after the system booting.
Furthermore, this problem occurs while the computer system is “awakened” from a power saving mode. Consequently, the LCD monitor operating under the digital display mode cannot display an analog video signal output from the computer main body.
On the other hand, though the LCD monitor is set by the analog display mode, if the graphic card outputs the digital signal when the computer system is performing system booting, the LCD monitor cannot display the system booting screen, and another monitor operating under the digital display mode is needed to input the password.